The information in the description is correct. DDR5 RAM uses the so-called Double Data Rate (DDR), which means that the effective data rate in MT/s is twice as high as the clock frequency in MHz. This means, for example, that 4000 MHz corresponds to 8000 MT/s. So when ASUS states 8000+ MT/s and the shop says 4000 MHz, they both mean the same performance - just expressed differently.